Site Records

Site Name: RAF Ventnor Chain Home Radar Station

[Source:
Nick
Catford - Historic information from ''Radar on the isle of Wight]

Following the development of radar at Orfordness
and at the Bawdsey
Research Station in Suffolk during the mid 1930's, the Air Ministry
established a programme of building radar stations around the British
coast to provide warning of air attack on Great Britain. A survey was
undertaken in 1938 to assess the suitability of the local terrain for
Air Defence Radar operations with the first of these new stations coming
on line by the end of the year. This network formed the basis of a chain
of radar stations called CHAIN
HOME (CH).

These stations consisted of two main types; East Coast stations
and West Coast stations. The East Coast stations were similar
in design to the experimental station set up at Bawdsey in 1936.

In their final form these stations were designed to have equipment
housed in protected buildings with transmitter aerials suspended
from 350' steel towers and receiver aerials mounted on 240' timber
towers.

RAF Ventnor - transmitter towers in the foreground

The West Coast stations differed in layout and relied on dispersal
instead of protected buildings for defence. Thus the West Coast stations
had two transmitter and receiver blocks with duplicate equipment in
each. Transmitter aerials were mounted on 325' guyed steel masts with
the receiver aerial mounted on 240' timber towers.

Ventnor was one of 20 CH stations authorised in 1937. The site, on
St. Boniface Down would give good long range performance but because
there was no level ground in front of the masts it wouldn't be capable
of height finding.

In order to provide immediate cover an 'advance' station was established
using experimental transmitters and receivers installed in temporary
hurts. Ventnor was one of eight such locations. Once the 240' receiver
towers were completed at the end of October 1938, the station went to
an 'intermediate' stage using the experimental equipment and temporary
aerials mounted on two of the towers. The intermediate station was operational
by 26th January 1939. The station went onto 24 hour watch from Easter
1939 and was put on a war footing on 24th August 1939

During this period, work continued on the final Chain Home installation
with the building of four 365' transmitter towers spaced 180ft apart
during the summer of 1939. This was later reduced to three. This was
because of the urgency involved in the Chain Home programme, the 'state
of the art' of prewar radio technology and the shortage of steel. It
was originally planned that each station would operate on four spot
frequencies in the 50-20 MHz range, (6-15 metre wave length), with the
transmitting aerials suspended between the platforms at 50, 200 and
350 feet. However, it was soon found that the radiation pattern was
not as good as it theoretically should have been and to overcome the
difficulty, a larger curtain array of dipoles and reflectors, suspended
on high tensile steel cables slung between towers, was the answer.

RAF
Ventnor in 1947

At the same time it was decided that four frequencies per station would
lead to delays and was, in any event, unduly optimistic of achievement.
The number of frequencies was reduced to two in the 30-22 MHz range,
(10 -13.5 metre bands). As two suspended arrays could be supported between
three towers, (the middle one being common to both arrays), those stations
still under construction would have one tower deleted. The fourth tower
was dismantled and shipped to Skaw in the Shetlands.

In October 1939 a Chain
Home Low station was also planned for Ventnor. This was to be built
by the army in a separate compound within the boundary of the Chain
Home Station. This station was to be known as Boniface Down with the
code number M86.

German
aerial photograph from September 1940 showing RAF Ventnor has been selected
as a target. The station is clearly visible in the centre of the picture
on top of St. Boniface Down

On 12th August 1940, four CH stations were selected for attack by
the Luftwaffe. After causing damage to the radar stations at Dover,
Rye and Pevensey
the bombers headed for Ventnor where they were intercepted at the start
of their raid. The station suffered considerable damage which forced
it off the air and most of the buildings were damaged or destroyed;
casualties were however light with only one soldier being injured.

Following this raid a mobile installation
was brought on to the island and set up at Bembridge. It was operational
from 23rd August 1940 and remained in use until the station was
repaired.

As a result of this attack, it was proposed by the Air Ministry
that the majority of Chain Home stations should be provided with
reserve equipment, either underground or remotely sited. Buried
reserves were provided at the more vulnerable stations (i.e. those
on the east and south coast) consisting of underground transmitter
and receiver blocks.

On some stations the transmitter and receiver buried reserves
were together on an adjoining site (often the next field).At others
the two buried reserves were separate but located close to their
respective above ground building.

Three of the four receiver towers at Ventnor

Many of the West Coast stations had remote reserves some distance from
the main station but utilising similar above ground transmitter and
receiver blocks. Most stations were powered from the National Grid but
they were also provided with generators to cover interruptions in the
mains electricity supply. Each reserve would also have a 120' wooden
aerial tower. While the reserves were under construction mobile radio
units were deployed as reserve stations.

Ventnor was provided with buried reserves located together close to
the southern perimeter fence. They were not ready for use until well
into 1942.